THE flu vaccine offered by GPs and private clinics is designed to protect people only against three existing human strains of the influenza virus, and will not confer immunity against the H5N1 avian flu that has killed at least 60 people in Asia.

Health officials, however, say that the detection of the H5N1 virus in Turkey, and possibly Romania, makes it even more important that vulnerable groups are vaccinated this year.

As well as protecting against ordinary flu viruses that will circulate this winter, widespread vaccination reduces the chance that people will become infected with seasonal influenza and avian flu at the same time.

Such co-infections are worry virologists as they increase the chances of the two flu genes swapping genes to create a new H5N1 strain that can spread easily from one person to another — the key step that could generate a pandemic.

Scientists still think it far more likely that such a strain of flu will emerge in Asia than in Europe, owing to the proximity with which birds live with people in countries such as Vietnam, Thailand and China.

Even so, wide participation in the seasonal flu vaccination programme will reduce the small risk of something similar happening should the H5N1 virus make it to Britain, and would ensure that elderly and infirm people are in more robust health if a pandemic were to strike.

Britain orders 14 million doses of seasonal flu vaccine each winter, which is usually administered this month as it takes several weeks to confer full immunity. It is available on the NHS to the over-65s and people who suffer from high-risk diseases such as asthma, diabetes and serious lung and heart conditions.

Vaccines can be given at a GP’s discretion, but will not normally be provided to people outside the high-risk groups. Many companies provide free annual flu shots to their employees, and private clinics also offer the jab, at a cost of about £25 a head.

Five companies supply the vaccine — Solvay, GlaxoSmithKline, Sanofi-Pasteur, Chiron and Wyeth. This year, the vaccine contains the New Caledonia H1N1 strain and the California H3N1 strain of influenza A, and the Shanghai strain of influenza B.

The pharmaceutical industry’s annual vaccine production capacity is about 300 million doses. It would be difficult for this to be scaled up quickly, as it has to be manufactured using fertilised chicken eggs and these sterile facilities take several years to be built up.

Britain has one flu vaccine plant, near Liverpool, which is owned by Chiron. It was shut down after contamination problems, but was cleared to resume production last month.

Experts such as Albert Osterhaus, of the Erasmus Medical Centre in Rotterdam, predict that countries in which vaccine factories are based would nationalise them in the event of a pandemic to secure a supply for their own populations.

No vaccine is yet available against H5N1 avian flu, although several candidate vaccines have been developed. The most fully tested, made by Sanofi-Pasteur, confers immunity only at very high doses.

This means that even if every vaccine factory were to be switched to making H5N1 vaccine, the world would be able to produce only about 75 million courses in all. Scientists are investigating ways of lowering the amount of vaccine needed for a shot.

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